JPH087456B2 - Dry developer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dry developer used for developing an electrostatic latent image in electrophotography and electrostatic recording.

(Prior Art) Dry developers can be roughly classified into a one-component developer using a toner itself in which a colorant is dispersed in a binder resin, and a two-component developer in which a carrier is mixed with the toner, After developing the electrostatic latent image formed on the photoconductor with these developers and transferring the toner on the photoconductor, the toner remaining on the photoconductor is to be cleaned. It is necessary to satisfy various conditions in the copying process, especially in the developing process or the cleaning process. In particular, the toner is not developed as an aggregate during development but is provided as individual particles for development. For this reason, the toner has sufficient fluidity, and the fluidity or electrical properties are changed over time. Alternatively, it is necessary that it does not change depending on the environment (temperature, humidity), and in the two-component developer, it is necessary to prevent development in which toner adheres to the carrier surface (so-called toner filming).
Further, it is necessary that the residual toner is easily separated from the surface of the photoconductor during cleaning and that the photoconductor is not damaged when used together with a cleaning member such as a blade or a web. In order to meet these requirements, dry developers include inorganic fine powder such as silica, fatty acid and its derivatives, organic fine powder such as metal salt, fluorine resin fine powder and the like as one-component developer or two-component developer externally added to the toner. Various developers have been proposed to improve fluidity, durability, cleaning properties, and the like.

(Problems to be Solved by the Invention) However, among the conventionally proposed external additives, silica,
Inorganic oxides such as titania and alumina remarkably improve the fluidity, but since they are considerably hard in themselves, the surface of the photoreceptor is dented or scratched, and there is a problem that the toner sticks to that portion. The cleaning method using a rubber blade or a brush is adopted for the organic belt photoconductor for high-speed machines. However, compared to the conventional drum photoconductor cleaning, the organic belt photoconductor is distorted or warped. However, there is a problem that the cleaning performance is remarkably deteriorated, and in particular, paper dust or the like enters between the photoconductor and the blade to induce cleaning failure. Furthermore, the recent demand for low-potential high-developing property has increased, and a low specific gravity, low magnetic force dispersion type carrier containing resin and magnetic powder as essential components is used. Such a carrier adheres to the surface of the photoconductor. However, there is a problem that the surface of the photoconductor is damaged during cleaning.

Therefore, the present invention solves the above problems, maintains good fluidity and cleaning properties, is excellent in environmental stability and durability, and prevents the toner filming phenomenon on the photoconductor or the carrier surface. The present invention is intended to provide a dry developer that can be used.

(Means for Solving the Problems) The present invention is a developer used in an electrophotographic method in which a rubber blade, a brush or the like is pressed against an organic belt photosensitive member for cleaning, and includes a dispersion type carrier having a resin and magnetic powder and a toner. In the constituted developer, polyethylene having a molecular weight of 10,000 or less, a density of 0.95 or more, and an average volume diameter of 15 μm or less is externally added to the toner or directly mixed with the developer to perform a dry developer. It is a dry developer characterized by the following.

The content of polyethylene contained in the dry developer is preferably 0.01 to 10% by weight based on the total weight of the toner. If it is less than 0.01% by weight, the cleaning property tends to decrease, and if it exceeds 10% by weight, the triboelectrification property of the toner tends to decrease and the developability tends to decrease.

The method of external addition to the toner may be simply mechanical mixing,
The adhesion may be such that it adheres loosely to the surface. Also,
The polyethylene fine powder may not cover the entire surface of the toner particles, or the fine powder may be partially covered as an agglomerate, but is preferably coated in a single-layer particle state.

The dry developer of the present invention is used as a two-component developer by mixing such toner with a dispersion type carrier. As a mixing procedure, the polyethylene fine powder may be externally added to the toner in advance and then mixed with the carrier, or the toner, the carrier and the polyethylene fine powder may be blended at the same time. Here, a V-blender, a Henshur blender, etc. can be used.

By the way, the toner is mainly composed of a binder resin and a colorant.

Examples of the binder resin used include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate,
Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, methacrylic acid Butyl, α-methylene aliphatic monocarboxylic acid esters such as dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether;
Homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone can be exemplified, and particularly typical binder resins include polystyrene and styrene-alkyl acrylate. Examples thereof include a copolymer, a styrene-alkyl methacrylate copolymer, a styrene-acrylonitrile copolymer, a styrene-butadiene copolymer, a styrene-maleic anhydride copolymer, polyethylene and polypropylene. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin and waxes can be mentioned.

Further, as the colorant, carbon black, aniline blue, calcoil blue, chrome yellow, ultralin blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue,
Malachite green oxalate, lamp black, rose bengal and the like can be exemplified as typical ones.

The toner is not limited to the binder resin and the colorant, and may include a charge control agent, a cleaning aid, and a fluidity accelerator, if necessary. Even if TiO ₂ , SiO ₂ , Al ₂ O ₃ or the like is externally added to improve the fluidity, the presence of the polyethylene coating prevents the inorganic particles from adhering to the photoconductor, so that scratches, etc. There is no problem.

Further, the toner in the present invention may be a magnetic toner containing a magnetic material or a capsule toner.

The toner of the present invention is about 30 μm or less, preferably 3 to 20 μm.
Those having an average particle size of μm can be used.

Next, the carrier is a dispersion type carrier composed mainly of resin and magnetic powder, and as the resin, all of those exemplified as the above-mentioned binder resin for toner can be used. Further, as the magnetic powder, fine particles of a commonly used ferromagnetic material can be used, and specifically, ferric tetroxide, γ-
Iron sesquioxide, various ferrites, chromium oxide, various fine metal powders and the like can be used. Furthermore, if necessary, a charge control agent or the like can be included. Make a carrier by kneading, pulverizing, classifying, etc. the above components,
The carrier may be prepared by liquefying the above components with a solvent or heating and spray drying or the like.

In the present invention, the carrier having an average particle diameter of about 20 to 400 μm, preferably 30 to 200 μm can be used.

(Function) The dry developer according to the present invention has a toner containing a binder resin and a colorant as main components, and a dispersion type carrier containing a resin and magnetic powder as main components, and has a molecular weight of 10,000 or less and a density. Polyethylene fine powder having a volume average particle diameter of 0.95 or less and an average volume diameter of 15 μm or less may be externally added to the toner in advance and then mixed with the carrier, or the above polyethylene may be added and mixed when the toner and the carrier are mixed.

The dry developer according to the present invention is applied to a high-speed developing method for developing a latent image that moves at a high speed, that is, an electrophotographic method for cleaning an organic belt photoreceptor by using a rubber blade, a flash, etc., By blending polyethylene, a lubricant effect is exerted, a lubricating film is formed on the surface of the photoreceptor, and white spots and fogging are less likely to occur in image quality. In order to form a lubricious film, the molecular weight of polyethylene must be 10,000 or less, and in order to prevent adhesion and fusion to the photoreceptor and exert the lubricant effect, the density is 0.95 or more. It is necessary to use one having an average volume diameter d ₅₀ of 15 μm or less, preferably 10 μm or less.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The present invention is not limited to these examples. In the following examples, "part" means "part by weight".

Example 1 Styrene-butyl acrylate copolymer (80/20) 100 parts Carbon black (Regal 330, Cabot) 10 parts Low molecular weight polypropylene (Viscor 660P, Sanyo Kasei) 5 parts Charge control agent (Bontron N-30 the Orient chemical Co., Ltd.) 1 part the above components were melt-kneaded in a Banbury mixer, and pulverized by a cooled jet mill, classified to an average volume diameter d ₅₀ of obtain a toner 11μm by further classifier of the finely pulverized product .

To 100 parts of this toner, 1 part of silica fine particles having an average volume diameter of 0.1 μm and 0.5 parts of polyethylene having an average volume diameter of 8 μm, a density of 0.97 and a molecular weight of 9000 (Ceridust 3620, manufactured by Hoechst) are dispersed and mixed by a blender. To prepare a toner.

On the other hand, as for the dispersion type carrier, the following components were melt-kneaded by a pressure kneader and further pulverized and classified by using a turbo mill and a classifier to obtain a carrier having an average volume diameter d ₅₀ of 50 μm.

The above toner and this carrier were mixed in a weight ratio of 5:95 to obtain a two-component developer.

Example 2 A toner having the same composition as in Example 1 was kneaded, pulverized and classified to obtain a toner having an average volume diameter of 11 μm. With respect to 100 parts of this toner, titanium oxide fine particles 1 having an average volume diameter of 0.1 μm
Parts, density 0.97, molecular weight 5000 polyethylene (200
(P, manufactured by Mitsui Petrochemical Co., Ltd.) 0.5 part of which was prepared by freezing and pulverization to an average volume diameter of 6 μm was dispersed and mixed by a blender,
A two-component developer was obtained in the same manner as in Example 1.

Example 3 An average volume diameter of 0.1 μ was added to 100 parts of a toner having an average volume diameter of 11 μm obtained by kneading and pulverizing and classifying the same composition as in Example 1.
1 part of titanium oxide fine particles with an average volume diameter of 6 μm and a density
0.5 part of polyethylene having a molecular weight of 6,000 (ACumist B6, manufactured by Allied Company) was dispersed and mixed by a blender, and then a two-component developer was obtained in the same manner as in Example 1.

Comparative Example 1 A two-component developer was obtained in the same manner as in Example 1 except that polyethylene fine particles were removed.

Comparative Example 2 A two-component developer was obtained in the same manner as in Example 1, except that 0.5 part of calcium stearate (average volume diameter 1 μm) having a lubricant effect was used in place of the polyethylene of Example 1.

Example 3 A two-component developer was obtained in the same manner as in Example 2, except that the average volume diameter of polyethylene of Example 2 was adjusted to 20 μm and used.

Comparative Example 4 Example 1 was repeated except that the polyethylene of Example 1 was replaced by freeze pulverization to prepare an average volume diameter of 8 μm, and 0.5 part of polyethylene having a density of 0.92 and a molecular weight of 5000 (220P, manufactured by Mitsui Petrochemical Co., Ltd.) was used. A two-component developer was obtained in the same manner.

Comparative Example 5 An example except that the polyethylene of Example 1 was adjusted to an average volume diameter of 9 μm by freeze pulverization, and 0.5 part of polyethylene having a density of 0.96 and a molecular weight of 40,000 (PE-190, manufactured by Hoechst) was used. A two-component developer was obtained in the same manner as in 1.

Copy Test An electrophotographic copying machine (FX507 manufactured by Fuji Xerox Co., Ltd.) was prepared using the dry developers obtained in Examples 1 to 3 and Comparative Examples 1 to 5 above.
When the continuous copying test was conducted in 5), the following results were obtained. As is apparent from this table, in the above-described embodiment, it is found that a stable charge amount can be obtained and good image quality is formed. Further, it can be seen that the cleaning property is excellent and there is no problem with the toner storage property.

(Advantages of the Invention) The present invention, by adopting the above-mentioned constitution, remarkably improves the cleaning property of the dry developer, is excellent in environmental stability and durability, and forms a proper polyethylene film on the photoreceptor, It is possible to suppress the toner filming phenomenon on the photoconductor, insufficient cleaning due to paper dust adhesion, and the like. In particular, when the high-speed developing method for developing a latent image moving at high speed is carried out in a system using an induction belt photosensitive member and a developer containing a dispersion type carrier, the above effect is remarkably exhibited.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuichi Kimura 1600 Takematsu, Minamiashigara City, Kanagawa Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Takayoshi Aoki 1600 Takematsu, Minamiashigara City, Kanagawa Fuji Xerox Co., Ltd. Takematsu Business In-house (56) Reference JP-A-1-177583 (JP, A) JP-A-63-61265 (JP, A) JP-A-64-54458 (JP, A) JP-A-57-84460 (JP, A)

Claims (1)

[Claims] 1. A developer used in an electrophotographic method in which a rubber blade, a brush or the like is pressed against an organic belt photosensitive member for cleaning, which is composed of a dispersion type carrier having a resin and magnetic powder, and a toner. Molecular weight 10,000 or less,
A dry developer, characterized in that polyethylene having a density of 0.95 or more and an average volume diameter of 15 μm or less is externally added to the toner or directly mixed with the developer.